Whereas the key lit=* indicates the presence of lighting, it is not always adequate to describe the perceived value of the lighting. There's a big difference between a highway lit with motorway type lighting fixtures, which emit plenty of light but with a poor Color rendering index, when compared to a way with far apart spaced and possibly dim Mercury-vapor lamps.

Values so far

Feel free to suggest more or better definitions. I'll come up with example pictures sometime.

lit:perceived=none: All one can see is the silhouette of their hand against the sky. Can appear on ways with lit=no.

lit:perceived=minimal: Only a minimal amount of light is present; one can see the ground if they're not an elderly person or otherwise visually impaired, but most people would have to focus on watching their steps. Can appear on ways with lit=no.